Finally, we arrive at the time of harvest! This represents 10 months of hard work, attention to detail, and refined cultivation techniques necessary for all the grapes to ripen.

The choice of the harvest date is influenced by many factors: the health of the cluster, the value of the sugars, total acidity and pH, but also - and especially for the red grapes - on the quality and quantity of the polyphenols from the grapes.

Before we get into the specifics of the ripening of the grapes though, we see that the cluster consists of the Vitis vinifera.

THE COMPOSITION OF THE WINE CLUSTER WITH RESPECT TO THE PROCESS

The cluster is composed of raspo (the grape stalk) and the berry, which in turn is made from the peel, pulp, and seeds (varying from 0 to 4 seeds):

Raspo: poor in sugar (10 per thousand), with an average of free acids, the presence of acids salified, pH > 4, and rich in polyphenols (22% of total);

Peel: poor in sugar, on average, with free acids, the presence of acids salified, pH > 4, rich in polyphenols (12% of total), and rich in odorous substances;

Pulp: rich in sugar, rich in organic acids and partially free of salified acids, pH < 4, shortage of polyphenols (1% of total), and rich in mineral salts and nitrogen compounds; and

Grape: rich in tannin (65% of the total).

As you can see, the composition of each part of the cluster differs, and each part brings to the future wine different compounds and essentials.

I’ll briefly describe these compounds, starting from the simplest to the most complex and arriving at polyphenols.

The sugar present in the berry is mainly represented by fructose and glucose. The relationship between these two sugars can be defined as mature in a 1:1 ratio. They are simple sugars (monosaccharides), both fermented by the yeast. The quantities are variable, but generally, to harvest the grapes requires a minimum of 160 grams per liter up to at most 250 to 280 grams per liter.

Organic acids are the backbone of the sour grape and are mainly comprised of tartaric, citric, and malic acids.

Tartaric acid is not fermentable by yeast and/or bacteria (except for rare cases) and represents the characteristic sour grape and the wine. Not being fermentable guarantees the longevity of the sour wine and its ability to age. The average amount of tartaric acid ranges from 3 to 7 grams per liter.

The second acid is malic acid, which is fermentable by lactic acid bacteria that transform as a result of this fermentation into lactic acid. The average quantity of malic acid ranges from 0.5 to 4 grams per liter and are smaller in warmer climates but higher in colder climates.

Last in order of importance is citric acid, which is also fermentable by lactic acid bacteria that transform it into acetic acid. It is present in small amounts, generally from 0.1 to 0.3 grams per liter.

The other components of the macroscopic cluster are mainly represented by potassium, calcium, and magnesium, and then by other macro and micro elements.

The berry is rich in vitamins, gives the aromas of the grapes, and contains dozens of other small components that also influence the complexity of the wine.

Now we enter into the complex world of polyphenols, those magic molecules that are capable of strongly characterizing the wine and are powerful antioxidants (i.e., they counteract the action of oxygen).

What follows is a scheme intended only to outline these complex molecules that interact in the chemical processes that determine the life of the wine, the organoleptic (or sensory) qualities of the wine, and at the end, the personality and identity of the wine itself. This article is not intended to analyze the individual phenolic compounds and explain how they interact.

Returning to our grapes, we can finally define the maturity of a grape and what characterizes a ripe grape that will produce a large, open red wine.

The ripe grape features:

Peels rich in anthocyanins and tannins that are complex in nature;

Grape seed medium-rich in polymerized tannins;

Presence of sugar to the optimal extent, around 230 grams per liter

Presence of a good heritage acid, about 6 to 7 grams per liter; and

Presence of a pH that is at least 3.3 to 3.4.

The unripe grape features:

Peels poor in anthocyanins and tannins of a relatively simple nature;

Grape seed rich in little polymerized tannins; and

For points c, d, and e above, values below those listed.

These are the values ​​that we want to obtain from the chemical point of view of winemaking. We can check these values after a thorough sampling of the grapes and a subsequent chemical analysis.

In addition to the chemical analysis, the task of the agronomist and winemaker is to carry out a visual inspection of the grapes, as well as a tasting, walking through the vineyards to assess acids at random. The tasting is as important as the chemical analysis, as tasting the grapes allows us to check the following:

The color and flavor of the peel;

To see if the skin stains the fingers, which signals the presence of the polyphenol anthocyanin;

To see if the pulp remains rigid or is loose. If it is loose, the pulp will easily break down into its component parts;

That the seeds are more brown than green (the more brown the better); and

Tasting/chewing the seeds releases coffee, chocolate, and toasted flavors but not flavors of the green pepper (vegetable).

While chemical analysis and tasting are crucial to deciding the harvest date, there is another factor to this decision that we cannot control: the weather. If the anticyclone helps us, we can work to research all these details, but if the rain haunts us, we have to collect a technological maturity and lower polyphenolic and still produce wines full of personality and territorial identity.